[PT Run] [Folder Plugin] Environment Variables With Autocomplete (#13811)

* search environment variables folders with autocomplete

* refactoring and tests

* fix

src/modules/launcher/Plugins/Microsoft.Plugin.Folder/EnvironmentVariableProcessor.cs

@@ -0,0 +1,39 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Microsoft.Plugin.Folder.Sources;
+using Microsoft.Plugin.Folder.Sources.Result;
+
+namespace Microsoft.Plugin.Folder
+{
+    public class EnvironmentVariableProcessor : IFolderProcessor
+    {
+        private readonly IEnvironmentHelper _environmentHelper;
+        private readonly IQueryEnvironmentVariable _queryEnvironmentVariable;
+
+        public EnvironmentVariableProcessor(IEnvironmentHelper environmentHelper, IQueryEnvironmentVariable queryEnvironmentVariable)
+        {
+            _environmentHelper = environmentHelper;
+            _queryEnvironmentVariable = queryEnvironmentVariable;
+        }
+
+        public IEnumerable<IItemResult> Results(string actionKeyword, string search)
+        {
+            if (search == null)
+            {
+                throw new ArgumentNullException(nameof(search));
+            }
+
+            if (!_environmentHelper.IsEnvironmentVariable(search))
+            {
+                return Enumerable.Empty<IItemResult>();
+            }
+
+            return _queryEnvironmentVariable.Query(search);
+        }
+    }
+}